The present invention pertains to a device for producing printed products comprising an arrangement of cooperating rollers and an apparatus for adjusting the axial spacing between two rollers.
Machines for processing paper and/or cardboard with an arrangement of several parallel rollers, which associated devices for adjusting the spacing of the rollers relative to one another, are generally known. For example, publication DE 602 14 133 T2 discloses such a machine in the form of a machine for producing corrugated cardboard. This machine comprises a first corrugating roller, which on the one hand meshes with a second corrugating roller in order to corrugate a paper web and on the other hand cooperates with a glue cylinder for applying glue onto the corrugation crests of the paper web, as well as a pressing roller that supplies a second paper web, wherein the axes of all aforementioned rollers and cylinders are arranged parallel to one another.
In order to adjust the gap between the glue cylinder and the first corrugating roller, the glue cylinder is supported in an oscillating crank construction that can be pivoted about axes extending parallel to the rollers. A pair of first cams is arranged above the plane defined by the axes of the glue cylinder and the first corrugating roller and serves as a stop for the oscillating crank construction, wherein said first cams can be adjusted independently of one another in order to achieve an exactly parallel alignment of the glue cylinder relative to the first corrugating roller. Furthermore, an additional cam is provided and arranged opposite of the pair of first cams referred to the aforementioned plane, wherein the additional cam allows the oscillating crank construction to pivot about the pair of first cams serving as a stop and thereby makes it possible to adjust the gap width.
The glue cylinder features an overrunning clutch and is driven in such a way that its circumferential speed is slightly slower than the circumferential speed of the corrugated paper web transported on the first corrugating roller. In this case, the overrunning clutch is equipped with sensors that monitor whether a driving torque is transmitted to the glue cylinder by means of the overrunning clutch. This makes it possible to indirectly monitor whether the glue cylinder is driven by means of the overrunning clutch or by means of the paper web transported on the first corrugating roller and therefore whether the gap width allows a glue transfer.
In order to adjust the desired gap width, the greatest gap width possible is initially adjusted by means of the additional cam and subsequently reduced while the machine is running until it is detected that the glue cylinder is driven by means of the corrugating roller. In this case, the actually adjusted gap width remains unknown such that this slow approach is required anew for each adjustment process and only can be carried out while the machine is running, but not at a standstill. Furthermore, such a gap width adjustment is heavily dependent on the material properties of the paper web, the glue cylinder and, if applicable, glue adhering to the glue cylinder. An excessive approach speed of the glue cylinder to the corrugating roller in connection with the sluggish information processing for the drive monitoring results in narrower gap widths than desired.
Apparatuses for adjusting rollers relative to one another in order to adjust the pressure acting upon a substrate located between the rollers are known from printing machines. In this context, publication EP 1 708 885 B1 proposes a roller bearing assembly that is composed of engaging cylinders, in the gap of which several pressure chambers are arranged distributed over the circumference. The purposeful actuation of these pressure chambers makes it possible to adjust the magnitude and the direction of the force acting upon the roller bearing assembly as a result of all pressure chambers. However, such a construction is elaborate and requires the additional use of a fluid.
In this case, the actual gap width between the rollers is also unknown and dependent on the material properties of the substrate to be printed. In addition, this type of force control can only be realized in the processing of endless webs because the processing of sheet material would inevitably cause the rollers to undesirably contact one another when a sheet exits the gap and to be abruptly pressed apart when a sheet enters the gap. This can lead to overshooting of the gap width and therefore damages to the rollers and the leading sheet edge at higher speeds.